Investigation On Welding Procedures And Welded Joint Properties Of 16Mn Steel By Twin Wiretandem Sequence Submerged Arc Welding Process

Twin-wire submerged arc welding is one of advanced and efficient welding methods,the introduction of two-wire can reduce the welding pass and increase welding productivity obviously,and it can control welding heat input in a wide range to meet the performance requirements under different conditions by adjusting the pre-and post-wire welding current.16Mn is,currently in China,one of the most widely used steels in shipbuilding,pressure vessels,bridges,rail vehicles, engineering machinery,pipelines,nuclear power station,marine structures and other areas.Although this steel has good weldability,but it has a litle tedency of quench hard and cold crack because of containing a certain amount of alloying elements such as carbon and manganese.While welding,The excessive welding heat input will lead to growth of grain or produce Widmanstatten in coarse-grain zone and reduce toughness of metal in that area,but reversely,it will abate the toughness for the increase of martensite proportion in coarse-grained zone under too small welding heat input.In this paper,engineer testing was executed under the condition of the same welding speed and the same heat input on 16Mn steel by using twin-wire and single-wire automatic submerged arc welding process respectively.Macro cross-sections of welded joint and deposition rate of wire metal that under different process were compared,it has analysed the microstructureof welded joints,tested the micro-hardness of weld joints,room temperature tensile,impact and high temperature tensile of weld joints were put to test.The results shows that:compared to single-wire submerged arc welding process,joints of twin-wire submerged arc welding process have a more reasonable shape,deeper weld penetration and wider weld width,deposition rate increase with the inhance of heat input under the condition of the same welding speed,deposition rate grows with the raise of welding speed under the condition of the same heat input,The twin-wire submerged arc welding process can significantly increase the deposition rate than single-wire submerged arc welding process,which can increase welding productivity obviously; microstructure of welded joints by twin-wire automatic submerged arc welding are ferrite and pearlite,but they are lager than that of single-wire ones,some of the region welded joint appears Widmanstatten ferrite,degree of supercooling reduce, the composition segregation phenomenon abates.Tensile strength and impact toughness of welded joints are slightly higher than that of the base metal,Tensile specimens of high temperature breaked at the zone of base metal,it shows that the mechanical property of welded joints at high-temperature is better than that of 16Mn. In this paper,Welding Procedures and welded Joint Properties of 16Mn Steel by Twin wire Tandem Sequence Submerged Arc Welding Process were studied,in the hope that it can provide basis for actual production and reference for further research.